The invention relates to a method for relief grinding the cutting teeth of taps, thread formers, and similar tools. The term “cutting tooth” shall also include the profile formers of thread formers.
The prior art includes such methods.
For instance, CH-PS 413 637 suggests a device suitable for this purpose in which a camshaft rotates continuously in the same direction. Two identically embodied cam disks with cams are provided on the camshaft. The cams for the two cam disks are offset from one another by 180 degrees. Positioned against each of the two cam disks is a scanning roller, these being coupled to one another via a parallelogram lever. The scanning movement for the scanning rollers is transmitted via another lever to an eccentric bearing for the grinding spindle. Depending on the position of the cams on the cam disks, the eccentric bearing of the grinding spindle is rotated so that a rotating grinding wheel is positioned with greater or less force against the tool to be ground. In this manner a relief is gradually created on a cutting tooth of the tool. One complete rotation of the camshaft and thus also of the cam disks corresponds to the grinding process on one cutting tooth. Provided for the transition to the next cutting tooth is a rapid return in which both scanning rollers temporarily lift from the cam disks.
Such direct mechanical scanning and transmission works relatively sluggishly. In addition, it is disadvantageous that the contour of the cam disks focuses on the undercut contour of a single cutting tooth. The cam disk must be exchanged if a tap, thread former, or similar tool is to be ground with a different undercut contour. However, cam disks are precision machine parts that must be machined with great accuracy and they are consequently expensive. Therefore, in addition to the time consumed for the required exchange of the cam disks, there is also the disadvantage that a large number of cam disks must be maintained in the inventory.
In order to alleviate this disadvantage, it has already been suggested in accordance with DE 29 52 610 C2 to provide, instead of a cam disk, a control roller, the surface of which has different profile depths along the roller axis. It should be possible to displace the control roller axially, even during the grinding process. In this manner it is possible to adjust the oscillation travel for a special relief grinding body that is also embodied adjustable as a part of the grinding table. The relief grinding body is positioned against the control roller by means of a scanning roller and is adjusted directly by this control roller. The relief grinding rate can be continuously adjusted when grinding with the grinding machine in accordance with DE 29 52 610 C2. However, in this case, as well, the drive shaft of the camshaft rotates continuously, and control roller must be exchangeable. A plurality of control cams can be embodied on the control roller, their teeth corresponding to the cutting teeth on the tool to be ground. However, for the grinding machine in accordance with DE 29 52 610 C2, for adapting to different required relief grinding shapes it is also expressly provided that different types of control rollers can be exchanged for one another. A special lifting device is provided for this. Also required is a gear unit with change gears that can be exchanged for one another as needed.
The machine in accordance with DE 29 52 610 C2 also suffers from the disadvantage of time-consuming dismantling and exchange processes in conjunction with maintaining an inventory of precision exchange parts.
Finally, known from DE 41 30 736 A1 is adjustably guiding a grinding spindle on a rotary table into two directions that are perpendicular to one another. For producing a relief on a securely clamped workpiece, the grinding spindle with a rotating grinding disk is forcibly guided by a guide rule. However, for producing different relief contours, in this case, as well, the guide rule must have different profiles, that is, it must be exchangeable.